Zone-Melting Recrystallization (ZMR) is a process for producing thin crystalline films of silicon (Si) isolated from a silicon substrate by a buried insulating layer, i.e., SiO.sub.2. In the ZMR process a layer of SiO.sub.2 is deposited on a substrate, often a single-crystal wafer. Polycrystalline Si (polysilicon) is then deposited on the SiO.sub.2 layer; followed by deposition of a capping layer or a wetting agent, such as SiO.sub.2.
This structure is then subjected to a heat treatment wherein the polysilicon film is melted.
Typically, the heating is performed using a stationary bottom heater adjacent the substrate surface. The stationary heater elevates the temperature of the polysilicon to about 1000.degree. C.-1300.degree. C., near its melting point. A movable upper heating source is then translated past the structure adjacent the capping film to supply sufficient heat to melt the polysilicon as the heating source moves along its path. Upon recrystallization the polysilicon film is transformed to a single, or nearly single crystalline film. Optionally, a single crystal seed material may be used to aid in epitaxial recrystallization. (See U.S. Pat. No. 4,371,421 to Fan et al., and "Silicon Graphoepitaxy Using a Strip-Heater Oven" by M. W. Geis et al., Appl. Phys. Lett., 37 (5) Sep. 1, 1980).
Silicon-on-Insulator material (SOI) prepared by the ZMR technique promises to satisfy the material needs for many important device applications, including radiation-hardened circuits, high voltage circuits, faster computating circuits, and microsensors, etc. Currently, however, ZMR processed SOI wafers have several significant material problems that can potentially limit their wide-spread adoption. The major problems are associated with one or more of the following: surface-edge defects, sub-boundary defects, surface defects, and "warp and slip".